Should Microsoft be targeting the Carriers in the Patent Wars?

Reading all this stuff about patent infringement of intellectual property lately I got to thinking. What about the Carriers? It can be said that they are simply transferring the stolen property from one entity to another. But once they take possession of an OS, and work their magic (basically adding useless crap) on it, have they not taken ownership of said OS. I thought possession was 90% of the law. And what about OS updates, where they get another opportunity to do even more tinkering. While physical characteristics of a device, like button placement, are on the OEM, the OS that the Carrier manipulates and calls their own seems to make them more than simply a facilitator.

Would be interesting to see Microsoft make one such claim. I bet the Carrier in-store shopping experience would change overnight. But maybe Microsoft wants to wait for Windows Phone to reach a 10-15% market share before ruffling those feathers.